With advances in drilling technology, it is currently possible to drill horizontal wellbores deep into hydrocarbon producing reservoirs. Utilization of horizontal wellbores allows extended contact with a producing formation, thereby facilitating drainage and production of the reservoir.
Although horizontal wellbores allow more contact with the producing formation, some difficulties are encountered when horizontal wellbores are utilized which are not commonly experienced when vertical wells are used. Methods used in producing hydrocarbons from a formation or reservoir via vertical wells often prove to be inefficient when attempting to remove hydrocarbons from a reservoir where horizontal wellbores are being used. This inefficiency results in utilization of increased amounts of fluids used during enhanced oil recovery operation. This results in a dimunition in the amount of hydrocarbons removed from the formation or reservoir.
This inefficiency is demonstrated when a carbon dixoide flood is utilized with a vertical wellbore where the formation contains zones of varying permeability. Often the carbon dioxide overrides a zone of lower permeability leaving hydrocarbonaceous fluids behind.
U.S. Pat. No. 4,736,792, issued to Brown et al. on Apr. 12, 1988, discloses a method for treating a well completed in a subterranean formation containing petroleum where a preconditioning process was employed. The preconditioning process was used to improve the receptivity of the formation to steam. The method involved injecting a heated non-condensible and oil soluble gas, in the gaseous phase, into the formation so as to avoid permanently fracturing the formation and also avoid the immediate formation of an oil bank.
Stephens in U.S. Pat. No. 4,607,699, issued Aug. 26, 1986, discusses a huff-puff cyclic steam stimulation method. Here a formation is fractured by liquid carbon dioxide injection. While carbon dioxide is still in place within the formation, steam is injected into the formation. After a suitable soaking period, the well is opened to production.
Therefore, what is needed is a method to improve the sweep efficiency of liquid carbon dioxide in a formation where only horizontal wellbores are utilized and the formation is not fractured.